df16c1c51d
Currently the phy reset sequence is as shown below for a
devicetree described mdio phy on boot:
1. Assert the phy_device's reset as part of registering
2. Deassert the phy_device's reset as part of registering
3. Deassert the phy_device's reset as part of phy_probe
4. Deassert the phy_device's reset as part of phy_hw_init
The extra two deasserts include waiting the deassert delay afterwards,
which is adding unnecessary delay.
This applies to both possible types of resets (reset controller
reference and a reset gpio) that can be used.
Here's some snipped tracing output using the following command line
params "trace_event=gpio:* trace_options=stacktrace" illustrating
the reset handling and where its coming from:
/* Assert */
systemd-udevd-283 [002] ..... 6.780434: gpio_value: 544 set 0
systemd-udevd-283 [002] ..... 6.783849: <stack trace>
=> gpiod_set_raw_value_commit
=> gpiod_set_value_nocheck
=> gpiod_set_value_cansleep
=> mdio_device_reset
=> mdiobus_register_device
=> phy_device_register
=> fwnode_mdiobus_phy_device_register
=> fwnode_mdiobus_register_phy
=> __of_mdiobus_register
=> stmmac_mdio_register
=> stmmac_dvr_probe
=> stmmac_pltfr_probe
=> devm_stmmac_pltfr_probe
=> qcom_ethqos_probe
=> platform_probe
/* Deassert */
systemd-udevd-283 [002] ..... 6.802480: gpio_value: 544 set 1
systemd-udevd-283 [002] ..... 6.805886: <stack trace>
=> gpiod_set_raw_value_commit
=> gpiod_set_value_nocheck
=> gpiod_set_value_cansleep
=> mdio_device_reset
=> phy_device_register
=> fwnode_mdiobus_phy_device_register
=> fwnode_mdiobus_register_phy
=> __of_mdiobus_register
=> stmmac_mdio_register
=> stmmac_dvr_probe
=> stmmac_pltfr_probe
=> devm_stmmac_pltfr_probe
=> qcom_ethqos_probe
=> platform_probe
/* Deassert */
systemd-udevd-283 [002] ..... 6.882601: gpio_value: 544 set 1
systemd-udevd-283 [002] ..... 6.886014: <stack trace>
=> gpiod_set_raw_value_commit
=> gpiod_set_value_nocheck
=> gpiod_set_value_cansleep
=> mdio_device_reset
=> phy_probe
=> really_probe
=> __driver_probe_device
=> driver_probe_device
=> __device_attach_driver
=> bus_for_each_drv
=> __device_attach
=> device_initial_probe
=> bus_probe_device
=> device_add
=> phy_device_register
=> fwnode_mdiobus_phy_device_register
=> fwnode_mdiobus_register_phy
=> __of_mdiobus_register
=> stmmac_mdio_register
=> stmmac_dvr_probe
=> stmmac_pltfr_probe
=> devm_stmmac_pltfr_probe
=> qcom_ethqos_probe
=> platform_probe
/* Deassert */
NetworkManager-477 [000] ..... 7.023144: gpio_value: 544 set 1
NetworkManager-477 [000] ..... 7.026596: <stack trace>
=> gpiod_set_raw_value_commit
=> gpiod_set_value_nocheck
=> gpiod_set_value_cansleep
=> mdio_device_reset
=> phy_init_hw
=> phy_attach_direct
=> phylink_fwnode_phy_connect
=> __stmmac_open
=> stmmac_open
There's a lot of paths where the device is getting its reset
asserted and deasserted. Let's track the state and only actually
do the assert/deassert when it changes.
Reported-by: Sagar Cheluvegowda <quic_scheluve@quicinc.com>
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20231127-net-phy-reset-once-v2-1-448e8658779e@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.